1. Field of the invention
The present invention relates to a face milling cutter in which a plurality of cutter inserts are detachably mounted to an outer periphery of a forward end portion of a cutter body.
2. Prior art
A face milling cutter of the kind referred to above is known as shown, for example, in FIG. 1 of the accompanying drawings. The face milling cutter comprises a cutter body 1 which is adapted to be mounted to a main spindle of a milling machine or the like for rotation about a rotary axis O. The cutter body 1 is composed of a columnar shank 2 and a head 3 formed at a forward end portion of the shank 2. The head 3 is in the form of a disc having a relatively large thickness A plurality of cutter inserts 4 are detachably mounted to an outer periphery of a forward end portion of the head 3. Each of the cutter inserts 4 is in the form of a square plate.
The cutter insert 4 has four cutting edges 5a through 5d. A minor cutting edge 6 is formed between each pair of adjacent cutting edges. The cutting edge 5a serves as a major cutting edge which is inclined at 45.degree. with respect to the rotary axis O of the cutter body 1 in such a manner that the major cutting edge 5a approaches the rotary axis O as the distance increases from a rearward proximal end of the cutter body 1. That is, the major cutting edge 5a has a corner angle of 45.degree..
By the way, it is the state of things that when surface cutting is carried out by the use of the above-described face milling cutter, only a part, on the order of one half to a third, of the entire length of the major cutting edge 5a can be utilized, because of various restrictions including the power of the employed machine such as a milling machine or the like, the hardness of a workpiece, distortion of the workpiece due to cutting heat, and the like. Accordingly, an unused section remains in the major cutting edge 5a of the used cutter insert 4 to be disposed of. This is extremely uneconomical.
Further, even if the above-mentioned restrictions are overcome, the cutting operation by the use of the entire length of the major cutting edge 5a results in such a problem that chipping tends to occur at the minor cutting edge 6, because each pair of adjacent cutting edges intersect at a 90.degree. angle. In particular, such chipping also tends to occur at the minor cutting edge 6, when the cutter insert 4 is used to cut a recess in a workpiece.